Digital wireless audio transmission system with optimized dynamics

Abstract

A digital audio transmission system, in particular a wireless microphone or wireless pocket transmitter system. The audio transmission system has at least one wireless transmitter and at least one wireless receiver. The wireless transmitter has an analog input, a digitally adjustable input potentiometer for adjusting the input gain, an analog/digital converter for converting the analog signals into digital signals, a digital signal processing unit for performing digital signal processing, and a digital or a digitally adjustable output potentiometer for adjusting the output gain. The digital signal processing unit is adapted to adjust the gain of the digital input potentiometer and/or the digital output potentiometer in such a way that the dynamic range of the analog/digital converter is optimally utilized.

The invention claimed is: 
     
       1. A digital wireless audio transmission system comprising:
 at least one wireless transmitter; and 
 at least one wireless receiver; 
 wherein the wireless transmitter comprises:
 an analog input; 
 a digitally adjustable input potentiometer configured to adjust the input gain; 
 an analog/digital converter configured to convert analog signals into digital signals; and 
 a digital signal processing unit configured to perform digital signal processing; 
 
 wherein the digital signal processing unit is adapted to adjust a gain of the digital input potentiometer in such a way that a dynamic range of the analog/digital converter is optimally utilized; and 
 wherein the adjustment of the gain of the digitally adjustable input potentiometer is effected during a zero crossing of an acoustic useful signal. 
 
     
     
       2. The wireless audio transmission system as set forth in  claim 1 ;
 wherein the wireless transmitter further comprises:
 a digital or digitally adjustable output potentiometer; 
 
 wherein a gain of the digital or digitally adjustable output potentiometer is opposite to the gain of the input potentiometer. 
 
     
     
       3. The wireless audio transmission system as set forth in  claim 2 ;
 wherein the adjustment of the gain of the digital input potentiometer is effected in such a way that a number of effective bits which are used by the analog/digital converter, a subsequent signal processing system which has audio algorithms or codecs, and a digital/analog converter is increased; and 
 wherein the gain at the digital output potentiometer is adjusted to compensate for a shift in the gain at the input so that a gain of the overall system is not influenced by optimization of the dynamic. 
 
     
     
       4. The wireless audio transmission system as set forth in  claim 1 ;
 wherein:
 calibration is effected for the digitally adjustable input potentiometer; 
 corresponding calibration values are stored; and 
 the corresponding calibration values are taken into consideration when calculating the mirror-image correction of the signals. 
 
 
     
     
       5. The wireless audio transmission system as set forth in  claim 4 ;
 wherein the calibration operation is performed automatically by the digital signal processing unit disposed in the circuit. 
 
     
     
       6. The wireless audio transmission system as set forth in  claim 5 ;
 wherein the calibration operation is automatically repeated at fixed time intervals. 
 
     
     
       7. A digital audio transmission system comprising:
 at least one wireless transmitter; 
 and at least one wireless receiver; 
 wherein the wireless transmitter comprises:
 an analog input; 
 a digitally adjustable input potentiometer configured to adjust the input gain; 
 an analog/digital converter configured to convert the analog signals into digital signals; and 
 a digital signal processing unit configured to perform digital signal processing; 
 
 wherein the digital signal processing unit is adapted to adjust a gain of the digital input potentiometer in such a way that a dynamic range of the analog/digital converter is optimally utilized; 
 wherein, by virtue of an abrupt severe rise in amplitude of an acoustic useful signal, a fresh adjustment of the digitally adjustable input potentiometer is very rapidly effected to prevent overdriving; and 
 wherein the very rapid actuation of the digitally adjustable input potentiometer is effected by an interrupt routine of the digital signal processing unit or an additional hardware specifically adapted thereto. 
 
     
     
       8. A method of controlling a digital wireless audio transmission system;
 wherein the audio transmission system has:
 a wireless transmitter; and 
 a wireless receiver; 
 
 wherein the wireless transmitter has:
 an analog input; 
 a digitally adjustable input potentiometer configured to adjust the input gain; 
 an analog/digital converter configured to convert the analog signals into digital signals; and 
 a digital signal processing unit configured to perform digital signal processing; 
 
 wherein the method comprises the steps:
 adjusting a gain of the digital input potentiometer so that a dynamic range of the analog/digital converter is optimally used; 
 wherein adjustment of the digitally adjustable input potentiometer is effected during a zero crossing of an acoustic useful signal. 
 
 
     
     
       9. A method of controlling a digital wireless audio transmission system;
 wherein the digital wireless audio transmission system has: 
 a wireless transmitter; and 
 a wireless receiver; 
 wherein the wireless transmitter has: 
 an analog input; 
 a digitally adjustable input potentiometer configured to adjust the input gain; 
 an analog/digital converter configured to convert the analog signals into digital signals; and 
 a digital signal processing unit configured to perform digital signal processing; and 
 wherein the method comprises the steps: 
 adjusting a gain of the digital input potentiometer so that a dynamic range of the analog/digital converter is optimally used; 
 wherein, by virtue of an abrupt severe rise in amplitude of an acoustic useful signal, a fresh adjustment of the digitally adjustable input potentiometer is very rapidly effected to prevent overdriving; and 
 wherein the very rapid actuation of the digitally adjustable input potentiometer is effected by an interrupt routine of the internal digital processing unit or an additional hardware specifically adapted thereto, in particular a peak detector which reacts to positive and negative peaks. 
 
     
     
       10. The wireless audio transmission system as set forth in  claim 2 ;
 wherein:
 calibration is effected for the digitally adjustable output potentiometer; 
 corresponding calibration values are stored; and 
 the corresponding calibration values are taken into consideration when calculating the mirror-image correction of the signals. 
 
 
     
     
       11. The wireless audio transmission system as set forth in  claim 10 ;
 wherein the calibration operation is performed automatically by the digital signal processing unit disposed in the circuit. 
 
     
     
       12. The wireless audio transmission system as set forth in  claim 11 ;
 wherein the calibration operation is automatically repeated at fixed time intervals. 
 
     
     
       13. The digital audio transmission system as set forth in  claim 7 ;
 wherein the very rapid actuation of the digitally adjustable input potentiometer is effected by an interrupt routine of a peak detector that reacts to positive and negative peaks. 
 
     
     
       14. The method of controlling a digital wireless audio transmission system as set forth in  claim 9 ;
 wherein the very rapid actuation of the digitally adjustable input potentiometer is effected by an interrupt routine of a peak detector which reacts to positive and negative peaks. 
 
     
     
       15. The digital wireless audio transmission system as set forth in  claim 1 ;
 wherein said acoustic useful signal includes a signal that is input to the analog/digital converter. 
 
     
     
       16. The digital wireless audio transmission system as set forth in  claim 1 ;
 wherein said acoustic useful signal includes a signal that is output by the digitally adjustable input potentiometer. 
 
     
     
       17. The method of controlling a digital wireless audio transmission system as set forth in  claim 8 ;
 wherein said acoustic useful signal includes a signal that is input to the analog/digital converter. 
 
     
     
       18. The method of controlling a digital wireless audio transmission system as set forth in  claim 8 ;
 wherein said acoustic useful signal includes a signal that is output by the digitally adjustable input potentiometer. 
 
     
     
       19. A digital wireless transmitter comprising:
 an analog input amplifier; 
 a digitally adjustable input potentiometer receiving a signal from the analog input amplifier and being configured to adjust an input gain; 
 an analog/digital converter configured to convert an analog output signal of the digitally adjustable input potentiometer into a digital signal, wherein the analog/digital converter uses a clocked processing; 
 a peak detector configured to monitor the analog output signal of the digitally adjustable input potentiometer or the analog input signal of the analog/digital converter; and 
 a digital signal processing unit configured to perform digital processing of the digital signal provided by the analog/digital converter; 
 wherein the peak detector provides a signal to an interrupt input of the digital signal processing unit when a signal peak above a threshold is detected by the peak detector, and 
 wherein the digital signal processing unit, upon receiving said signal at said interrupt input, adjusts the digitally adjustable input potentiometer, independent of the clocked processing of the analog/digital converter. 
 
     
     
       20. The digital wireless transmitter as set forth in  claim 19 ;
 wherein the digital signal processing unit, upon receiving said signal at said interrupt input, adjusts the digitally adjustable input potentiometer before a next clock cycle of the analog/digital converter's processing. 
 
     
     
       21. The digital wireless transmitter as set forth in  claim 19 , further comprising:
 a zero crossing detector configured to monitor the output signal of the digitally adjustable input potentiometer or an input signal of the analog/digital converter, 
 wherein the zero crossing detector controls adjustment of the digitally adjustable input potentiometer to be performed during a zero crossing of the monitored signal. 
 
     
     
       22. The digital wireless transmitter as set forth in  claim 19 ;
 wherein the digital signal processing unit further comprises a gain compensation unit adapted to compensate the input gain applied by the digitally adjustable input potentiometer. 
 
     
     
       23. A digital wireless microphone comprising a digital wireless transmitter as set forth in  claim 19 . 
     
     
       24. A digital wireless transmitter comprising:
 an analog input amplifier; 
 a digitally adjustable input potentiometer receiving a signal from the analog input amplifier and being configured to adjust an input gain; 
 an analog/digital converter configured to convert an analog output signal of the digitally adjustable input potentiometer into a digital signal, wherein the analog/digital converter uses a clocked processing; 
 a zero crossing detector configured to monitor the analog output signal of the digitally adjustable input potentiometer or the analog input signal of the analog/digital converter; and 
 a digital signal processing unit configured to perform digital processing of the digital signal provided by the analog/digital converter; 
 wherein the zero crossing detector provides a signal to an interrupt input of the digital signal processing unit when a change of a sign of the monitored signal is detected by the zero crossing detector, and 
 wherein the digital signal processing unit, upon receiving said signal at said interrupt input, adjusts the digitally adjustable input potentiometer, independent of the clocked processing of the analog/digital converter. 
 
     
     
       25. The digital wireless transmitter as set forth in  claim 24 ;
 wherein the digital signal processing unit, upon receiving said signal at said interrupt input, adjusts the digitally adjustable input potentiometer before a next clock cycle of the analog/digital converter's processing. 
 
     
     
       26. A digital wireless microphone comprising a digital wireless transmitter as set forth in  claim 24 .